This application relies for priority upon Korean Patent Application No. 2001-20767, filed on Apr. 18, 2001, the entire contents of which are hereby incorporated herein by reference for all purposes as if fully set forth herein.
The present invention generally relates to semiconductor manufacturing facilities, and more specifically to a power management system associated with semiconductor manufacturing facilities for preventing operational malfunctions due to transient interruption or suspension of AC power.
Transient power interruption, or suspension, may happen from various causes, for example, an unstable power supply environment in a local area, or an intentional severance of a power supply line (or cable) for power maintenance work. When AC power supplied through a power line temporarily goes down to a low level due to such transient power interruption, loading devices or equipment at a consumer""s side will malfunction or be out of order.
Several techniques for preventing malfunctions due to a transient power interruption have been disclosed in U.S. Pat. No. 5,216,897, Japanese Patent Publication Heisei 12-102195 and Heisei 11-178245, and Korean Patent Application 1998-021364. In U.S. Pat. No. 5,216,897, applicable to an air conditioning system, circuits reducing delay times by predetermined periods are employed to prevent an abnormal voltage drop due to a simultaneous supply of power to plural air conditioners at a time of power recovery. The Japanese Patent Publication 12-102195 proposes a mechanism for preventing malfunctions in loading devices which raises the voltage of a battery, converts the increased voltage into AC power through an inverter, and then applies the AC power to the loading devices. Meanwhile, the Japanese Patent Publication 11-178245, including a DC link circuit for receiving a DC voltage converted from a converter, a subsidiary condenser, and a switching circuit, controls input/output current operations with the switching circuit in order to prevent malfunctions of loading devices. The Korean Patent Application 1998-021364 prevents malfunctions of loading devices by utilizing a rectifier, a condenser, and a diode, and prevents a voltage drop due to an excessive current flow by blocking a power supply from loading devices consuming a lot of power by means of a reverse-biased diode when the power supply recovers.
A transient power interruption, or suspension, is generally defined as a feature of time that lasts less than 1 second from power shut-off until power recovery. When a time interval without power lasts longer than 1 second, it is regarded as a long-term power interruption, or suspension, that is distinguishable from the transient power interruption, or suspension.
FIG. 1 shows a conventional power supply system for semiconductor manufacturing facilities. The system is operable in 3-phase 208V AC power provided from a power distributor. Referring to FIG. 1, the system includes: a motor 23; an inverter (or a frequency converter) 21 controlling the speed of the motor 23; a heater 27; and a solid-state relay (so-called, SSR) 25 controlling power on/off operations for the heater 27; a compressor 31; cutoff devices 15, 17, and 19, protecting the aforementioned devices from overload, a power relay 5 to cut off the supply of AC power from the distributor; an emergency power cutoff circuit 3; and PLC (programmable logic controller) 11 for controlling the loading devices such as the motor 23, the heater 27, and the compressor 31.
It is required for the power supply system of FIG. 1 to be provided according to a specific design rule in order to be operable in a normal condition even during transient power interruption. For instance, a magnetic contactor (MC, so-called, xe2x80x9cpower relayxe2x80x9d) must maintain a turned-on state for 1 second, and all loading control devices (e.g., PLC, and digital meters) must maintain a turned-on state for 1 second. Further, in a main control system for operating peripheral devices cooperated with a reaction chamber in a general semiconductor manufacturing process, a feedback signal for checking an operation status of a chiller must maintain an active state for 1 second. If transient power interruption occurs under insufficient conditions with the necessary design rules, the power relay 5 is tripped open and all the loading control devices are shut down by being situated out of an input power range. Moreover, the feedback signal is disabled at the same time as the devices"" shutdown. As a result, the chiller cannot be operable in a normal state, thereby causing an increase in temperature in the reaction chamber and damage to semiconductor products.
FIGS. 2A, 2B, and 2C shows operational states of the power supply system of FIG. 1, relative to a waveform of AC power transmitted through a power cable, powering states of all the loading control devices, and waveforms of feedback signals transferred to a main control system from a chiller, respectively. While the AC power is 100% fully supplied to the facilities, all loading devices start to be conductive with a run switch turned on. At some time after that, if a power drop (or voltage drop) occurs due to, e.g., an accident at a power transmitter, then the AC power is not further supplied thereto through the power cable, and the power level drops to 0% as shown in FIG. 2A. Then, all the control devices stop their operations as shown in FIG. 2B. Therefore, the feedback signals, as shown in FIG. 2C, for representing current operation states of the chiller are disabled. If the time between power recovery at t2 and the power drop at t1 is less than 1 second, it is a transient power interruption. All operations of the loading devices are shut down during the period of the transient power interruption. Afterwards, when the power recovers and the run switch is turned on, all the devices in the facilities start to operate. On the other hand, the next power drop occurs at t3 and lasts beyond 1 second, that is, it is a long-term power suspension. The loading devices are also shut down. The next power recovery at t4 and the turning-on of run switch at t5 enable the loading devices to be operable. A stop switch at t6 forces termination of work in the overall facilities.
Accordingly, in a semiconductor manufacturing facility, the conventional power supply system is shut down when transient power interruption occurs, which is very disadvantageous in semiconductor manufacturing procedures, causing problems such as an increase of temperature in a reaction chamber due to a disabled chiller, resulting in damage to semiconductor products, and degradation of processing efficiency.
It is, therefore, an object of the present invention to provide a power management system capable of preventing a shut-off or malfunction of devices in manufacturing facilities even when transient power interruption, or suspension, occurs.
It is another object of the present invention to provide a power management system capable of stabilizing process conditions in semiconductor manufacturing facilities even when transient power interruption occurs.
In order to attain the above objects, according to an embodiment, a power management system includes an emergency cutoff circuit, a first power controller, and a second power controller. The emergency cutoff circuit controls a main power relay in order to maintain a supply of AC power for a predetermined period when transient power interruption, or suspension, occurs. The first power controller is charged up with a DC voltage provided from a rectifier (or a converter), and discharges the DC voltage for a predetermined time when an AC power is not supplied through a power supply line thereto due to transient power interruption. The second power controller receives the DC voltage provided from the first power controller at the first coil and outputs a predetermined operation voltage at the second coil during transient power interruption. The second power controller determines a holdup time (a time that a charge voltage at the first coil reaches the output voltage at the second coil, i.e., a minimum operation voltage) when an AC power supply is shut down due to transient power interruption, using a charge voltage of the first power controller and the DC voltage at the first coil.
A power management system including the emergency cutoff circuit and the first and second power controllers is installed in a chiller of semiconductor manufacturing facilities, as an exemplary practice.
Thus, even while transient power interruption occurs at for example local areas in which power supply condition is unstable, it is possible to secure normal processing operations in a semiconductor manufacturing facilities because process inertia and hold-up times increase through the emergency cutoff circuit and the first and second power controllers.
The foregoing features and advantages of the invention will be more fully described in the accompanying drawings.